1. Field of the Invention
This invention relates to an electronic part mounted on a circuit board, and more particularly to a technique effective for preventing a flux with which terminals of an electronic part are coated from intruding into the electronic part.
2. Statement of the Related Art
When an electronic part such as a relay, for example, is soldered and mounted onto a circuit board, in order to improve the wetness of a solder, such a flux treatment is adopted that terminals are coated with a flux in a state where the electronic part is temporarily jointed to the circuit board as a prerequisite step of the solder treatment. In short, the flux treatment is adopted to remove oxide layers from the terminals by the flux, to preserve the cleanness of the surface by preventing their repeated oxidation and to lower the surface tension of an interface at the time of the solder treatment, to thereby improve the wetness.
However, since the flux is corrosive, when the flux with which the terminals are coated intrudes into the electronic part due to the capillarity by the surface tension, in a case of a relay, for example, on-off failure of a contact point and the like takes place as described in Japanese Utility Model Laid-Open No. 63-82335.
In order to prevent the above-described problem, the flux has heretofore been prevented from intruding by sealing portions of the terminals which are close to a casing by use of a sealing material.
However, with the above-described technique, an additional step for sealing the terminals is required, and thus causes the production inefficiency. Furthermore, the sealing material is needed, whereby the costs are increased accordingly.